Rules are being developed for controlling a formant synthesizer (HLsyn) in
which ten higher-level parameters control changes in vocal-tract natural
frequencies, areas of four orifices, and other aspects of articulation. The
input to the rules is a phonetic sequence labeled in terms of distinctive
features. The rules operate in four stages. First, the time locations of a
sequence of landmarks are established. The landmarks are of three types:
locations of vowel nuclei and offglides, locations of amplitude minima for
glides, and times of formation and release of consonantal constrictions. Second,
formant trajectories between vowel landmarks are derived. Third, these
vowel-to-vowel formant movements are modified by the effects of consonantal
constrictions, working from left to right. Fourth, the effects of secondary
consonant articulations are added, including introduction of a velopharyngeal
opening, spreading or constricting glottal movements, and influences of
segmentally related vocal fold stiffening and vocal tract expansion or
contraction for obstruents. Trajectories of the parameters are, for the most
part, constructed from quarter-cycle segments of sinusoids. Examples of
synthesis of simple VCVCV utterances illustrate the vowel-to-vowel
coarticulation and context-dependent vowel formants that result from application
of the rules. [Supported in part by NIH Grant No. MH52358.]